1. Field of the invention
The present invention relates to a piezoelectric single phase uni-polar ultrasonic actuator, particularly to a uni-polar ultrasonic actuator that has a PZT (Pb(Zr0.52,Ti0.48)O3) plate and an upper back disc with several combinations of notch and/or screw thereon, so as to enable the actuator to operate at a single phase in an ultrasonic frequency range with a high efficient output.
2. Description of the Prior Art
FIG. 1 shows the structure of a conventional ultrasonic piezoelectric actuator. As can be seen, the structure in FIG. 1 consists of a circular disc shaped piezoelectric vibrator plate 1 as a driving member. This piezoelectric plate 1 is essentially a metallic back disc 11 made of nickel alloy on which a PZT plate 12 formed of PZT is adhered. The electrode unit 13 on the disc is divided in two electrodes 131 and 132 driven by two driving circuits respectively. As soon as an ultrasonic sinusoidal voltage is applied to PZT plate 12, the PZT plate 12 and its associated metallic back disc 111 vibrate with a high frequency. The energy thereof is transmitted sinusoidally with an amplitude in the range of μms controlled according to the strength of the input voltage. By so the structure is able to serve as a precise actuator. But a conventional PZT actuator constructed as such has several inherent disadvantages:
1.The fixed unadjustable output limits its application field.
2.An extra cost is required for dividing the electrode unit in two.
3.The PZT plate formed of PbTiO3 or PbZrO3 is very fragile.
It is what the reason the inventor has endeavored for years of continuous research and experimentation attempting to find out the remedy to palliate the inherent shortcomings of the conventional techniques described above, and at last has succeeded in realizing the present invention.